Turbo mileage gets new charge

By By Bob Weber

Aug 25, 2012 | 12:00 AM

It is almost like getting extra horsepower for free. At least that is how some people describe what a turbocharger can do for an engine these days.

In the past, turbochargers added extra zip but at the expense of consuming much more gas than non-turbocharged engines. But technological innovations have changed all that. Today's turbochargers offer increased fuel economy by outfitting cars with smaller engines allowing them to get the power of a bigger one on demand.

"With fuel prices being a significant concern for consumers and businesses, turbochargers are a smart choice for getting more miles to the gallon," said Tony Schultz, vice president for the Americas,

Honeywell

Turbo Technologies.

Turbocharged vehicles, such as Ford's EcoBoost lineup and the Chevrolet Sonic and Chevrolet Cruze have been among the best-selling vehicles in the U.S. this year. The Cruze Eco and Sonic, which both offer Honeywell turbocharged engines among its models, can deliver 40 mpg or higher on the highway and have starting prices below $20,000. The newly-released 2013 Dodge Dart with 160 horsepower also has a turbo.

In a recent report, the

Environmental Protection Agency

cited turbocharging as one technology helping explain "the improvements in CO2 and fuel economy during the last seven years" by making engines more efficient. A smaller turbocharged engine can provide 20 percent to 40 percent better fuel economy while delivering the performance of a larger engine. Industry data illustrates the ongoing downsizing trend as the average engine size in North America is decreasing from 3.6 liters in 2007 to a projected average 2.9 liters by 2016.

Although the technology is quite old (the first turbo was developed by Alfred Buchi, a Swiss engineer, in 1909) many people still don't understand what a turbocharger does.

Besides increasing the power output from an engine, a turbo helps conserve fuel since larger engines use more gas, and weigh more. When extra power isn't needed from a turbo, the engine operates in its naturally aspirated, fuel-sipping state.

Since 2008, there has been a decline in large 8-cylinder engines and an increase in 4-cylinder engines, according to J.D. Power and Associates partner firm LMC Automotive. Turbochargers were fitted in only two percent of gasoline or flex-fuel vehicles produced in the United States in 2008, but that figure jumped to 9.5 percent in 2011 and is expected to more than double to 23.5 percent in 2017, LMC Automotive predicts.

Turbocharger use spinning up

Honeywell estimates the number of turbocharged commercial and passenger vehicles sold in North America will reach 3.2 million in 2012, up from 2.2 million in 2011. Passenger vehicles alone account for nearly 850,000 additional turbo engines — a 61 percent increase from 2011.

What's the magic behind all this turbocharging? Exhaust leaving the engine is used to drive the turbo. Waste gases become an asset.

Simply, a turbocharger is a compressor, or pump, that forces more air into an engine than the engine can draw in on its own.

A naturally aspirated engine — one without a turbo — relies on vacuum created as the piston travels down the cylinder to suck air into that cylinder. The amount of air determines how much fuel can be burned. The ideal ratio is about 15 pounds of air per each pound of fuel.

If we can squeeze more air into the cylinder, we can add more fuel. That makes more power.

Think of the turbocharger as a two-sided pinwheel with a partition between pinwheels. Blow on one side of the pinwheel and the other spins. Exhaust gases leaving the engine go into a curved housing where they spin a turbine wheel. On the other side of the housing there is a compressor wheel. Fresh air enters the compressor and is pumped into the engine, more fuel is injected and power increases.

"It's a proven technology that can be used across market segments and does not put the consumer in an extended payback period like other technologies to realize its benefits," said Honeywell's Schultz.